Toll-like receptors (TLRs) form a large family of pattern recognition receptors with at least 11 members in human and 13 in mouse. TLRs recognize a wide variety of microbial components and potential hostderived agonists that have emerged as key mediators of innate immunity. TLR signaling also plays an important role in the activation of the adaptive immune system by inducing proinflammatory cytokines and upregulating costimulatory molecules of antigen presenting cells. The dysregulation of TLR signaling may cause autoimmunity. This review discusses the contribution of TLR signaling to the initiation and progression of autoimmune diseases, such as rheumatoid arthritis, experimental autoimmune encephalitis, myocarditis, hepatitis, kidney disease, systemic lupus erythematosus, diabetes, obesity, and experimental autoimmune uveitis as well as aging. The involvement of TLR signaling in the pathogenesis of autoimmune diseases may provide novel targets for the development of therapeutics.